První roky výzkumu řízené termojaderné fúze probíhaly ve znamení lineárních nebo toroidálních Z-pinčů, stelarátorů a tokamaků. Základním problémem všech projektů byly nestability, které bránily dosažení potřebných teplot, a vzájemná informační opona mezi laboratořemi v USA, UK a SSSR. Článek popisuje situaci ve třech zemích a hledá odpověď na otázku: "Z-pinč, tokamak - blízcí příbuzní? Kde se jejich cesty rozdělily?", The early years of thermonuclear fusion research used both linear and/or toroidal Z-pinches, stellarators and tokamaks. We discuss in this paper the basic problem of instabilities preventing formation of the required temperature and also the information curtain between US, UK and USSR laboratories. We also try to answer the question "Where exactly did the roads of Z-pinch and tokamak divide?"., Milan Řípa., and Obsahuje bibliografii
Melatonin, the main hormone of the pineal gland, informs the body about the environmental light and darkness regimen, which in turn contributes to the photoperiodic adaptation of several physiological functions. Leptin, the hormone secreted mainly by adipocytes and some other tissues including the pituitary, informs the brain about the mass of adipose tissue, which plays an important role in energy homeostasis. Melatonin has been shown to decrease circulating leptin levels. It is currently not known whether melatonin has an effect on leptin synthesis in the pituitary. The aim of this study was to immunohistochemically examine the effects of pinealectomy and administration of melatonin on leptin production in the rat anterior pituitary. The pituitary samples obtained from 18 male Wistar rats including sham-pinealectomized, pinealectomized and melatonin-injected pinealectomized groups were immunohistochemically evaluated. Immunostaining of leptin was moderate (3+) in sham-pinealectomized rats, heavy (5+) in pinealectomized rats and low (1+) in melatonin-treated pinealectomized rats, respectively. The present results indicate that pinealectomy induces leptin secretion in anterior pituitary cells, and this increase of leptin synthesis can be prevented by administration of melatonin. Thus, melatonin seems to have both physiological and pharmacological effects on leptin production in the anterior pituitary of male rats.
The global-scale natural experiment created by the widespread dissemination of most of the 111 species of pines (genus Pinus, family Pinaceae) has shed light on many aspects of plant invasion ecology. Introductions and the fate of alien pines have been well documented worldwide, facilitating the accurate labelling of species as “naturalized”, “invasive”, or “non-invasive” using objective criteria. Thirty species are naturalized and 21 are invasive. Three life-history traits that clearly separate invasive from non-invasive taxa define the inherent ability of species to disperse over long distances, win in competition against other plants, and to survive or proliferate under a range of disturbance regimes. The realization of colonization opportunities for potentially invasive pines is determined by extrinsic factors, especially those that mediate seedling establishment. Meta-analysis of many introduction/invasion events revealed the interplay of factors. Detailed studies of pine invasions have elucidated the roles of long-distance seed dispersal and propagule pressure in driving invasions. Enhanced understanding of the ecology of pine invasions has improved our ability to manage these invasions. No other speciose genus of plants has yielded important insights on so many facets of invasion ecology.